Method and Apparatus for Adjusting Operating Parameters of a Vacuum Pump Arrangement

ABSTRACT

A method for adjusting operating parameters of a vacuum pump arrangement includes determining characteristics of a gas flowing through the vacuum pump arrangement; and setting operating parameters of the vacuum pump arrangement based on the determined characteristics of the first gas. A controller can be configured to perform the method for adjusting the operating parameters of the vacuum pump arrangement in accordance with the characteristics of the gas.

CROSS-REFERENCE TO RELATED APPLICATION

This Application is a Section 371 National Stage Application of International Application No. PCT/GB2013/051025, filed Apr. 23, 2013, which is incorporated by reference in its entirety and published as WO 2013/171454 A1 on Nov. 21, 2013 and which claims priority of British Application No. 1208735.9, filed May 18, 2012.

BACKGROUND

This invention relates to a method and/or apparatus for adjusting the operating parameters of a vacuum pump arrangement, and more particularly to a method and/or apparatus for self-adjusting the power or temperature limits of the vacuum pump arrangement based on the thermal characteristics of the gas flowing through the vacuum pump arrangement.

A system used in semiconductor or other industrial manufacturing processes typically includes, among other things, a process tool, a vacuum pump arrangement having a booster pump and a backing pump, and an abatement device. In semiconductor manufacturing applications, the process tool typically includes a process chamber, in which a semiconductor wafer is processed into a predetermined structure. The vacuum pump arrangement is connected to the process tool for evacuating the process chamber to create a vacuum environment in the process chamber in order for various semiconductor processing techniques to take place. The gas evacuated from the process chamber by the vacuum pump arrangement might be directed to the abatement device, which destroys or decomposes harmful or toxic components of the gas before it is released to the environment.

Many semiconductor processing techniques are associated with injecting various gases into the process chamber at different steps. Hydrogen is one of the commonly used gases in processes, such as Metalorganic Chemical Vapor Deposition (MOCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), and silicon epitaxy. The gases that are rich in hydrogen often exhibit very different characteristics from those including heavier gaseous components. The gas with a large proportion of hydrogen tends to have a high thermal conductivity, whereas the gas with a large proportion of heavy gaseous components tends to have a lower thermal conductivity. When the hydrogen rich gas is pumped through a vacuum pump, the temperature differential between the rotor and the stator tends to be smaller than that when the gas contains a large proportion of heavy gaseous components. As a result, there is a lower risk for a vacuum pump pumping the hydrogen rich gas to seize due to a clash between the rotor and the stator caused by thermal expansion, as opposed to a vacuum pump pumping heavy gases.

Despite the well controlled risk of pump seizure, vacuum pumps used in semiconductor manufacturing processes are often not driven as hard as they can be. Besides hydrogen, other heavier gases are also present in various steps in many semiconductor manufacturing process cycles. In order to accommodate those heavier gases, the power limits of the vacuum pumps are often set conservatively in order to avoid pump seizure caused by a clash between the rotor and the stator. As a result, the vacuum pumps tend to be underutilized.

Moreover, setting temperature limits for vacuum pumps based on the thermal characteristics of the heavy gases tends to cause frequent nuisance tripping when the vacuum pumps are pumping hydrogen rich gases. The temperature of a vacuum pump is almost always monitored from the outside of the pump casing, whereas the critical temperatures inside the vacuum pump are inferred from the outside temperature. It is a common industry practice to set the limit conservatively based on the outside temperature of the vacuum pump in order to avoid the internal temperatures exceeding a predetermined safety level. Due to the high thermal conductivity of hydrogen, the temperature differential between the outside and the inside of the vacuum pump tends to be smaller when the vacuum pump is pumping the hydrogen rich gas as opposed to the heavy gases. Because the internal temperature of a vacuum pump tends to be higher than the temperature on the outside, a limit set based on the thermal characteristics of the heavy gases might be too conservative for hydrogen-rich pumped gases. When the vacuum pump is pumping the hydrogen rich gas, such limit can be easily exceeded, while there is little risk for the pump to seize. This leads to nuisance tripping or a false alarm being triggered.

Conventionally, it might be possible to adjust the rotational speed of the vacuum pumps in response to the state of the process chamber. An example can be found in U.S. Pat. No. 6,739,840, which is directed to a method for controlling the vacuum pumps based on a signal provided by an upstream process tool that indicates whether or not the process chamber is in operation for the purpose of reducing the power consumption of the vacuum pumps. However, such a method does not take into account the chemistry and other characteristics of the gases evacuated from the process chamber for the purpose of extracting maximum performance out of the vacuum pumps. Neither does it provide the capability of adjusting the power and/or temperature limits of the vacuum pumps based on the signal generated by the process tool.

As such, what is needed is a method and/or apparatus for adjusting the operating parameters of the vacuum pump based on the thermal characteristics of the gas currently flowing through the vacuum pump.

The Summary is provided to introduce a selection of concepts in a simplified form that are further described in the Detail Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

SUMMARY

The disclosure is directed to a method for adjusting operating parameters of a vacuum pump arrangement, comprising: determining characteristics of a first gas flowing through the vacuum pump arrangement; and setting operating parameters of the vacuum pump arrangement based on the determined characteristics of the first gas.

The disclosure is also directed to an apparatus comprising: a process tool having a process chamber; a vacuum pump arrangement for evacuating the process chamber; and a controller configured to set operating parameters of the vacuum pump arrangement in response to information representing characteristics of a first gas flowing through the vacuum pump arrangement.

The construction and method of operation of the invention, however, together with additional objectives and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

The Summary is provided to introduce a selection of concepts in a simplified form that are further described in the Detail Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic view of a system where a process chamber, a booster pump, and a backing pump are connected in series in accordance with some embodiments of the invention.

FIG. 2 illustrates a flow chart showing a method for self-adjusting the operating parameters of the booster pump and the backing pump in accordance with some embodiments of the invention.

FIG. 3 illustrates a graph comparing the power consumption curves of the vacuum pumps in various conditions in accordance with some embodiments of the invention.

DETAILED DESCRIPTION

This disclosure is directed to a method and/or apparatus for adjusting the operating parameters of a vacuum pump arrangement in response to a signal indicative of the thermal characteristics of the gas being evacuated from a process tool upstream of the vacuum pump arrangement, or a determination of the thermal characteristics of the gas flowing through the vacuum pump arrangement based on power consumption patterns of the vacuum pump arrangement. The operating parameters of the vacuum pump arrangement can be adjusted in response to the signal received by the vacuum pump arrangement from a process tool that indicates the chemistry and thermal characteristics of the gas being evacuated from the process tool. Absent such signal, the thermal characteristics of the gases can be determined by analyzing the power consumption patterns, since different gases generate different power consumption patterns as they flow through the vacuum pump arrangement.

FIG. 1 illustrates a schematic view of a system 10 where a process chamber 12 and a vacuum pump arrangement 20 are connected in series in accordance with some embodiments of the invention. The vacuum pump arrangement 20 draws gases out of the process chamber 12 and creates a vacuum environment in it to carry out certain processes, such as depositions, etching, ion implantation, epitaxy, etc. The gases can be introduced into the process chamber 12 from one or more gas sources, such as the ones designated by 14 a and 14 b in this figure. The gas sources 14 a and 14 b can be connected to the process chamber 12 via control valves 16 a and 16 b, respectively. The timing of introducing various gases into the process chamber can be controlled by selectively turning on or off the control valves 16 a and 16 b. The flow rates of the gases introduced from the gas sources 14 a and 14 b into the process chamber 12 can be controlled by adjusting the fluid conductance of the control valves 16 a and 16 b. As discussed above, many semiconductor processing techniques, such as MOCVD, PECVD, and silicon epitaxy, often inject hydrogen rich gases into the process chamber 12 at one step, and other heavier gases at other steps. By “hydrogen rich,” it is understood that the hydrogen component in the gas is 50% or more in mole fraction or 7% or more in mass fraction.

The vacuum pump arrangement 20 includes a booster pump 22 and a backing pump 24 connected in series. The inlet of the booster pump 22 is connected to the outlet of the process chamber 12. The outlet of the booster pump 22 is connected to the inlet of the backing pump 24. The outlet of the backing pump 24 might be connected to an abatement device (not shown in the figure) where the exhaust gases emitted from the backing pump 24 are treated in order to reduce the harmful impact the exhaust gases might have on the environment. Sensors (not shown in the figure) can be implemented in the vacuum pump arrangement 20 to collect data of various measurements, such as the temperatures, power consumptions, pump speeds, etc., of the booster pump 22 and the backing pump 24. Sensors can also be implemented to measure the gas pressures at the inlets and/or outlets of the booster pump 22 and/or the backing pump 24. A controller 30 can be implemented to adjust the parameters of the vacuum pump arrangement 20 in response to a signal indicating the chemistry and thermal characteristics of the gas being evacuated from the process chamber 12. Such signal might be generated by a process tool incorporating the process chamber 12, or a remote host computer monitoring and controlling the process tool via a local area network or the Internet. Such signal might indicate a change of process recipe in the process chamber 12, and causes the controller 30 to adjust the parameters of the vacuum pump arrangement 20 accordingly. Additionally, one or more sensors (not shown) disposed on the foreline connecting the chamber 12 and vacuum pump arrangement 20 can be employed to determine the nature or characteristic of the gas being evacuated from the chamber 12.

Alternatively, the controller 30 can be implemented in the vacuum pump arrangement 20 in the form of a control circuit, which can analyze the data to obtain power consumption patterns of the vacuum pump arrangement 20, and set the operating parameters of the vacuum pump arrangement 20 according to the power consumption patterns.

FIG. 2 illustrates a flow chart 100 showing a method for self-adjusting the operating parameters of the vacuum pump arrangement 20 in accordance with some embodiments of the invention. FIG. 3 illustrates an exemplary graph comparing the power consumption curves of the booster pump 22 and the backing pump 24 in various conditions. Referring to FIGS. 2 and 3, initially at step 102, the booster pump 22 and backing pump 24 are set at the hydrogen operating parameters suitable for pumping gases that are rich in hydrogen. The hydrogen operating parameters compared to the heavy gas operating parameters can have higher power or temperature limits. As discussed above, the hydrogen rich gas has a high thermal conductivity, which leads to a low temperature differential between the inside and outside of a vacuum pump, and therefore permits the vacuum pump to be driven harder.

Step 104 determines whether the power consumption of the booster pump is greater than a first predetermined threshold. If the power consumption is below the first predetermined threshold, the process goes back to the beginning of step 104. If the power consumption is above the first predetermined threshold, the process proceeds to step 106. Step 106 determines whether the power consumption of the backing pump is below a second predetermined threshold. If the power consumption is above the second predetermined threshold, the process goes back to the beginning of step 104. If the power consumption is below the second predetermined threshold, the process proceeds to step 108 where the booster pump and the backing pump are set to the heavy gas operating parameters.

As shown in FIG. 3, the power consumption curve of the booster pump pumping hydrogen is designated by 202, whereas the power consumption curve of the booster pump pumping air is designated by 204. The power consumption curve of the backing pump pumping hydrogen is designated by 208, whereas the power consumption curve of the backing pump pumping air is designated by 206. Here, hydrogen and air are used as the proxies of the hydrogen rich gas and heavy gas, respectively, for the purposes of explaining the process illustrated in FIG. 2. The x-axis represents the gas pressure at the inlet of the vacuum pump arrangement that is constructed by the serially connected booster pump and backing pump. The y-axis represents the power consumptions of the booster pump and the backing pump. The first and second predetermined thresholds are represented by horizontal lines designated by 210 and 212, respectively. At pressure P1, if hydrogen is pumped through the booster pump and the backing pump, the power consumption of the booster pump will fall below the first predetermined threshold 210, and the hydrogen operating parameters will remain unchanged. However, if air is pumped through the booster pump and the backing pump, at pressure P1, the power consumption of the booster pump will be higher than the first predetermined threshold 210, while the power consumption of the backing pump will be below the second predetermined threshold 212. As such, the booster pump and the backing pump will be set to the heavy gas operating parameters.

After the booster pump and the backing pump are set to the heavy gas operating parameters at step 108, the process proceeds to step 110 where the power consumption of the booster pump is compared to a third predetermined threshold. If the power consumption of the booster pump is above the third predetermined threshold, the process goes back to the beginning of the step 110. If the power consumption of the booster pump is below the third predetermined threshold, the process proceeds to step 112 where the speed of the booster pump is compared to a predetermined speed threshold. If the speed of the booster pump is slower than the predetermined speed threshold, the process goes back to the beginning of step 110. If the speed of the booster pump exceeds the predetermined speed threshold, the process goes back to step 102 where the booster pump and the backing pump are reset to the hydrogen operating parameters.

As shown in FIG. 3, the third predetermined threshold is represented by a horizontal line designated by 214. There are two regions in the graph where the power consumptions of the booster pump are below the third predetermined threshold, namely region 220 where the pressure is below P2 and region 222 where the pressure is above P3. If the booster pump is in region 220, its speed would exceed the predetermined speed threshold, and therefore it would be safe to reset the booster pump and the backing pump back to the hydrogen operating parameters. However, if the booster pump is in region 222, its speed would be slower than the predetermined speed threshold, due to the high pressure at the inlets of the pumps. In such condition, it is not safe to reset the pumps to the hydrogen operating parameters, because they would drive the pumps too hard, therefore risking their exceeding the safety limits.

The disclosed method is capable of adjusting the parameters of the vacuum pump arrangement based on the data collected from the vacuum pump arrangement. If it is determined that the hydrogen rich gas is being pumped through the vacuum pump arrangement, the hydrogen operating parameters will be employed to drive the vacuum pump arrangement harder than when the heavy gas operating parameters are used. This enables the vacuum pump arrangement to operate at a greater capacity, without risking the vacuum pump arrangement exceeding its power or temperature limits.

Alternatively, the operating parameters of the vacuum pump arrangement can be adjusted in response to a signal indicating the chemistry and thermal characteristics of the gas being evacuated from the process chamber to the vacuum pump arrangement. As shown in FIG. 1, the controller 30 can be configured to adjust the operating parameters in response to such signal. The controller 30 can be implemented as a stand-alone device or an integral part of the vacuum pump arrangement 20. In some embodiments of the invention, the signal might be generated by the process tool incorporating the process chamber 12. In some other embodiments of the invention, the signal might be generated by a host computer remotely monitoring and controlling both the process tool and the vacuum pump arrangement via a local area network, or the Internet. Also, the signal might be generated by one or more sensors disposed in the foreline between the chamber and vacuum pump arrangement.

In some semiconductor manufacturing processes, a vacuum pump arrangement is used to pump both the hydrogen rich gas and the heavy gas at various steps. Conventionally, if the vacuum pump arrangement is designed according to the hydrogen gas flow, the size of the vacuum pump arrangement would need to be large in order to avoid pump seizure when it pumps the heavy gases. Unlike the conventional designs, the disclosed method and apparatus enables the vacuum pump arrangement to adjust or self-adjust its power or temperature limits in response to the thermal characteristics of the gas flowing through the arrangement. Thus, it enables the vacuum pump arrangement to be made in a smaller size, without compromising on its pumping capacity when it pumps the hydrogen rich gas or risking seizure when it pumps the heavy gas.

In addition to using the relationship between the power consumption and the inlet gas pressure to determine the thermal characteristics of the gas flowing through a vacuum pump arrangement, other relationships can also be used to make the determination. For example, the relationship between the power consumption and the pump speed might be used to determine the thermal characteristics of the gas flowing through the vacuum pump arrangement. As another example, the relationship between the power consumption and temperature of the pumps might be used to determine the thermal characteristics of the gas flowing through the vacuum pump arrangement. It is understood that setting the operating parameters of the vacuum pump arrangement based on those relationships can be achieved by applying the process illustrated in FIG. 2, with certain modifications accounting for the different curve patterns in those relationships. It is asserted that those modifications are within the scope of the present disclosure.

Although the invention is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention, as set forth in the following claims. 

1. A method of adjusting operating parameters of a vacuum pump arrangement, comprising: determining characteristics of a first gas flowing through the vacuum pump arrangement; and setting operating parameters of the vacuum pump arrangement based on the determined characteristics of the first gas.
 2. The method of claim 1, wherein the determining characteristics of the first gas comprises a step for the vacuum pump arrangement to receive a signal indicative of the characteristics.
 3. The method of claim 2, wherein the signal is provided from a process tool upstream of the vacuum pump arrangement.
 4. The method of claim 2, wherein the signal is generated by a sensor in a foreline connecting a process tool to the vacuum pump arrangement downstream thereof.
 5. The method of claim 4, wherein the senor is configured to make direct or indirect measurements of thermal conductivity of the first gas.
 6. The method of claim 1, wherein the determining characteristics of the first gas comprises: monitoring a property of the vacuum pump arrangement, as the vacuum pump arrangement pumps the first gas therethrough; and determining the characteristics of the first gas based on the monitored property.
 7. The method of claim 6, wherein the property is a power consumption pattern.
 8. The method of claim 1, wherein the vacuum pump arrangement comprises a booster pump and a backing pump serially connected to a process chamber in a manner that the booster pump is downstream of the process chamber and upstream of the backing pump.
 9. The method of claim 8, wherein the determining characteristics of the first gas comprises determining whether a power consumption of the booster pump at a given moment is above a first predetermined threshold.
 10. The method of claims 8, wherein the determining characteristics of the first gas comprises determining whether a power consumption of the backing pump at the given moment is below a predetermined second threshold, if the power consumption of the booster pump at the given moment is above the first predetermined threshold.
 11. The method of claim 10, wherein the determining characteristics of the first gas comprises designating the first gas as a heavy gas if the power consumption of the backing pump is below the second predetermined threshold and the power consumption of the booster pump is above the first predetermined threshold at the given moment.
 12. The method of claims 10, wherein the operating parameters are set to be heavy gas operating parameters in accordance with characteristics of the heavy gas if the power consumption of the backing pump is below the second predetermined threshold and the power consumption of the booster pump is above the first predetermined threshold at the given moment.
 13. The method of claim 10, wherein the determining characteristics of the first gas comprises designating the first gas as a hydrogen rich gas if the power consumption of the backing pump is above the second predetermined threshold and the power consumption of the booster pump is above the first predetermined threshold at the given moment.
 14. The method of claim 10, wherein the operating parameters are set to be hydrogen operating parameters in accordance with characteristics of the hydrogen rich gas if the power consumption of the backing pump is above the second predetermined threshold and the power consumption of the booster pump is above the first predetermined threshold at the given moment.
 15. The method of claims 13, wherein the hydrogen operating parameters have a power limit for the vacuum pump arrangement higher than that of the heavy gas operating parameters.
 16. The method of claims 13, wherein the hydrogen operating parameters have a temperature limit for the vacuum pump arrangement higher than that of the heavy gas operating parameters.
 17. The method of claim 12, wherein the determining characteristics of the first gas comprises determining whether the power consumption of the booster pump is below a third predetermined threshold.
 18. The method of claim 17, wherein the determining characteristics of the first gas comprises determining whether the booster pump exceeds a predetermined speed threshold, if the power consumption of the booster pump is below the third predetermined threshold.
 19. The method according to any of claims 17, wherein the operating parameters are set to be hydrogen operating parameters in accordance with characteristics of the hydrogen rich gas, if the booster pump exceeds the predetermined speed threshold and the power consumption of the booster pump is below the third predetermined threshold.
 20. The method according to claim 7, wherein the power consumption pattern comprises a relationship between a power consumption of the vacuum pump arrangement and an inlet pressure of the vacuum pump arrangement.
 21. The method according to claim 7, wherein the power consumption pattern comprises a relationship between a power consumption of the vacuum pump arrangement and a pump speed of the vacuum pump arrangement.
 22. The method according to claim 7, wherein the power consumption pattern comprises a relationship between a power consumption of the vacuum pump arrangement and a temperature of the vacuum pump arrangement.
 23. An apparatus comprising: a process tool having a process chamber; a vacuum pump arrangement for evacuating the process chamber; and a controller configured to set operating parameter of the vacuum pump arrangement in response to information representing characteristics of a first gas flowing through the vacuum pump arrangement.
 24. The apparatus of claim 23, wherein the information is in a form of a signal generated by the process tool.
 25. The apparatus of claim 24, wherein the signal is generated by a sensor in a foreline connecting the process tool to the vacuum pump arrangement downstream thereof.
 26. The apparatus of claim 25, wherein the senor is configured to make direct or indirect measurements of thermal conductivity of the first gas.
 27. The apparatus of claim 23, wherein the information is in a form of a monitored property of the vacuum pump arrangement.
 28. The apparatus of claim 27, wherein the monitored property comprises a power consumption pattern.
 29. The apparatus of claim 28, wherein the vacuum pump arrangement comprises a booster pump and a backing pump serially connected to a process chamber in a manner that the booster pump is downstream of the process chamber and upstream of the backing pump. 